A. The Iguanodonts: Iguanodon, Camptosaurus.
Sub-Order Ornithopoda or Iguanodontia.
In the early days of geology, about the middle of the nineteenth century, bones and footprints of huge extinct reptiles were found in the rocks of the Weald in south-eastern England. They were described by Mantell and Owen and shown to pertain to an extinct group of reptiles which Owen called the Dinosauria. So different were these bones from those of any modern reptiles that even the anatomical learning of the great English palaeontologist did not enable him to place them all correctly or reconstruct the true proportions of the animal to which they belonged. With them were found associated the bones of the great carnivorous dinosaur Megalosaurus; and the weird reconstructions of these animals, based by Waterhouse Hawkins upon the imperfect knowledge and erroneous ideas then prevailing, must be familiar to many of the older readers of this handbook. Life size restorations of these and other extinct animals were erected in the grounds of the Crystal Palace at Sydenham, London, and in Central Park, New York. Those in London still exist, so far as the writer is aware, but the stern mandate of a former mayor of New York ordered the destruction of the Central Park models, not indeed as incorrect scientifically, but as inconsistent with the doctrines of revealed religion, and they were accordingly broken up and thrown into the waters of the Park lake. Small replicas of these early attempts at restoring dinosaurs may still be seen in some of the older museums in this country and abroad.
Fig. 26.—Skeleton of Camptosaurus, an American relative of the Iguanodon.
The real construction of the Iguanodon was gradually built up by later discoveries, and in 1877 an extraordinary find in a coal mine at Bernissart in Belgium brought to light no less than seventeen skeletons more or less complete. These were found in an ancient fissure filled with rocks of Comanchic age, traversing the Carboniferous strata in which the coal seam lay, and with them were skeletons of other extinct reptiles of smaller size. The open fissure had evidently served as a trap into which these ancient giants had fallen, and either killed by the fall or unable to escape from the pit, their remains had been subsequently covered up by sediments and the pit filled in to remain sealed up until the present day. These skeletons, unique in their occurrence and manner of discovery, are the pride of the Brussels Museum of Natural History, and, together with the earlier discoveries, have made the Iguanodon the most familiar type of dinosaur to the people of England and Western Europe.
Fig. 27.—Teeth of the duck-billed dinosaur Trachodon. The dental magazine has been removed from the lower jaw and is seen to consist of several close-set rows of numerous small pencil-like teeth which are pushed up from beneath as they wear off at the grinding surface.
Camptosaurus. The American counterpart of the Iguanodons of Europe was the Camptosaurus, nearly related and generally similar in proportions but including mostly smaller species, and lacking some of the peculiar features of the Old World genus. In the National Museum at Washington, are mounted two skeletons of Camptosaurus, a large and a small species, and in the American Museum a skeleton of a small species. It suggests a large kangaroo in size and proportions, but the three-toed feet, with hoof-like claws, the reptilian skull, loosely put together, with lizard-like cheek teeth and turtle beak indicate a near relative of the great Iguanodon.
Thescelosaurus. The Iguanodont family survived until the close of the Age of Reptiles, with no great change in proportions or characters. Its latest member is Thescelosaurus, a contemporary of Triceratops. Partial skeletons of this animal are shown in the Dinosaur Hall; a more complete one is in the National Museum.
FOOTNOTES:
[15] Trachodont teeth never drop out, they are completely consumed. Only in the Iguanodonts and Ceratopsia are they shed.—B. Brown.
Chapter VII.[ToC]
THE BEAKED DINOSAURS (Continued).
B. The Duck Billed Dinosaurs,—Trachodon, Saurolophus, etc.
Sub-Order Ornithopoda; Family Trachodontidæ.
These animals of the Upper Cretaceous are probably descended from the Iguanodonts of an older period. But the long ages that intervened, some millions of years, have brought about various changes in the race, not so much in general proportions as in altering the form and relations of various bones of skull and skeleton and perfecting their adaptation to a somewhat different habit of life, so that they must be regarded as descendants perhaps, but certainly rather distant relatives, of the older group.
We know more about the Trachodonts than any other dinosaurs. For not only are the skeletons more frequently found articulated, but parts of the skin are not uncommonly preserved with them, and in one specimen at least, so much of the skin is preserved that it may fairly be called a "dinosaur mummy." This specimen of Trachodon is in the American Museum, and beside it are two fine mounted skeletons of the largest size. There is also on exhibition a panel mount of a nearly related genus, Saurolophus the skeleton lying as it was found in the rock, and a fine skeleton of a third genus Corythosaurus with the skin partly preserved on both sides of the crushed and flattened body stands beside it. In the Tyrannosaurus group when completed will appear a fourth skeleton of the Trachodon. Several skulls and incomplete skeletons on exhibition and other skeletons not yet prepared add to the Museum collection of this group. Trachodon skeletons may also be found in the Museums of New Haven, Washington, Frankfurt-on-the-Main, London and Paris, but nowhere a series comparable to that displayed at the American Museum.
THE TRACHODON GROUP.
The following description of the Trachodon group is by Mr. Barnum Brown and first appeared in the American Museum Journal for April 1908:[16]
"This group takes us back in imagination to the Cretaceous period, more than three millions of years ago, when Trachodonts were among the most numerous of the dinosaurs. Two members of the family are represented here as feeding in the marshes that characterized the period, when one is startled by the approach of a carnivorous dinosaur, Tyrannosaurus, their enemy, and rises on tiptoe to look over the surrounding plants and determine the direction from which it is coming. The other Trachodon, unaware of danger, continues peacefully to crop the foliage. Perhaps the erect member of the group had already had unpleasant experiences with hostile beasts, for a bone of its left foot bears three sharp gashes which were made by the teeth of some carnivorous dinosaur.
Fig. 28.—Mounted Skeletons of Trachodon in the American Museum. Height of standing skeleton 16 feet, 10 inches.
"By thus grouping the skeletons in lifelike attitudes, the relation of the different bones can best be shown, but these of course are only two of the attitudes commonly taken by the creatures during life. Mechanical and anatomical considerations, especially the long straight shafts of the leg bones, indicate that dinosaurs walked with their limbs straight under the body, rather than in a crawling attitude with the belly close to the ground, as is common among living reptiles.
"Trachodonts lived near the close of the Age of Reptiles in the Upper Cretaceous and had a wide geographical distribution, their remains having been found in New Jersey, Mississippi and Alabama, but more commonly in Wyoming, Montana, and the Dakotas. A suggestion of the great antiquity of these specimens is given by the fact that since the animals died layers of rock aggregating many thousand feet in vertical thickness have been deposited along the Atlantic coast.
"The bones of the erect specimen are but little crushed and a clear conception of the proportions of the animal can best be obtained from this specimen. It will be seen that the Trachodon was shaped somewhat like a kangaroo, with short fore legs, long hind legs, and a long tail. The fore limbs are reduced indeed to about one-sixth the size of the hind limbs and judging from the size and shape of the foot bones the front legs could not have borne much weight. They were probably used in supporting the anterior portion of the body when the creature was feeding, and in aiding it to recover an upright position. The specimen represented as feeding is posed so that the fore legs carry very little of the weight of the body. There are four toes on the front foot but the thumb is greatly reduced and the fifth digit or little finger, is absent." (Subsequent discoveries have shown that the arrangement of the digits made by Marsh and followed in this skeleton is incorrect. It is the first digit that is absent, and the fifth is reduced.)
"The hind legs are massive and have three well developed toes ending in broad hoofs. The pelvis is lightly constructed with bones elongated like those of birds. The long deep compressed tail was particularly adapted for locomotion in the water. It may also have served to balance the creature when standing erect on shore. The broad expanded lip of bone known as the fourth trochanter, on the inner posterior face of the femur or thigh bone was for the attachment of powerful tail muscles similar to those which enable the crocodile to move its tail from side to side with such dexterity. This trochanter is absent from the thigh bones of land-inhabiting dinosaurs with short tails, such as Stegosaurus and Triceratops. The tail muscles were attached to the vertebrae by numerous rod-like tendons which are preserved in position as fossils on the erect skeleton. Trachodonts are thought to have been expert swimmers. Unlike other dinosaurs their remains are frequently found in rocks that were formed under sea water probably bordering the shores but nevertheless containing typical sea shells.
"The elaborate dental apparatus is such as to show clearly that Trachodonts were strictly herbivorous creatures. The mouth was expanded to form a broad duck-like bill which during life was covered with a horny sheath, as in birds and turtles. Each jaw is provided with from 45 to 60 vertical and from 10 to 14 horizontal rows of teeth, so that there were more than 2000 teeth altogether in both jaws.
"Among living saurians, or reptiles, the small South American iguana Amblyrhynchus may be compared in some respects with the Trachodons notwithstanding the difference in size. These modern saurians live in great numbers on the shores of the Galapagos Islands off the coast of Chile. They swim out to sea in shoals and feed exclusively on seaweed which grows on the bottom at some distance from shore. The animal swims with perfect ease and quickness by a serpentine movement of its body and flattened tail, its legs meanwhile being closely pressed to its side and motionless. This is also the method of propulsion of crocodiles when swimming.
"The carnivorous or flesh-eating dinosaurs that lived on land, such as Allosaurus and Tyrannosaurus, were protected from foes by their sharp biting teeth, while the land-living herbivorous forms were provided with defensive horns, as in Triceratops, sharp spines as in Stegosaurus or were completely armored as in Ankylosaurus. Trachodon was not provided with horns, spines or plated armor, but it was sufficiently protected from carnivorous land forms by being able to enter and remain in the water. Its skin was covered with small raised scales, pentagonal in form on the body and tail, where they were largest, with smaller reticulations over the joints but never overlapping as in snakes or fishes. A Trachodon skeleton was recently found with an impression of the skin surrounding the vertebrae which is so well preserved that it gives even the contour of the tail as is shown in the illustration (fig. 32).
"During the existence of the Trachodonts the climate of the northern part of North America was much warmer than it is at present, the plant remains indicating a climate for Wyoming and Montana similar to what now prevails in Southern California. Palm leaves resembling the palmetto of Florida are frequently found in the same rocks with these skeletons. Here occur also such, at present, widely separated trees as the gingko now native of China, and the Sequoia now native of the Pacific Coast. Fruits and leaves of the fig tree are also common, but most abundant among the plant remains are the Equisetae or horsetail rushes, some species of which possibly supplied the Trachodons with food.
After Osborn
Fig. 29.—Restoration of the Duck-billed Dinosaur Trachodon. This restoration, made by Mr. Knight under supervision of Professor Osborn, embodies the latest evidence as to the structure and characteristic poses of these animals, the character of the skin and their probable habits and environment.
"Impressions of the more common plants found in the rocks of this period with sections of the tree trunks showing the woody structure will be [have been] introduced into the group as the ground on which the skeletons stand. In the rivers and bayous of that remote period there also lived many kinds of Unios or fresh-water clams, and other shells, the casts of which are frequently found with Trachodon bones. The fossil trunk of a coniferous tree was found in Wyoming, which was filled with groups of wood-living shells similar to the living Teredo. These also will be introduced in the ground-work.
"The skeleton mounted in a feeding posture was one of the principal specimens in the Cope Collection, which, through the generosity of the late President Jesup, was purchased and given to the American Museum. It was found near the Moreau River, north of the Black Hills, South Dakota, in 1882, by Dr. J.L. Wortman and Mr. R.S. Hill, collectors for Professor Cope. The erect skeleton came from Crooked Creek, central Montana, and was found by a ranchman, Mr. Oscar Hunter, while riding through the bad lands with a companion in 1904. The specimen was partly exposed, with backbone and ribs united in position. The parts that were weathered out are much lighter in color than the other bones. Their large size caused some discussion between the ranchmen and to settle the question, Mr. Hunter dismounted and kicked off all the tops of the vertebrae and rib-heads above ground, thereby proving by their brittle nature that they were stone and not buffalo bones as the other man contended. The proof was certainly conclusive, but it was extremely exasperating to the subsequent collectors. Another ranchman, Mr. Alfred Sensiba, heard of the find and knowing that it was valuable 'traded' Mr. Hunter a six-shooter for his interest in it. The specimen was purchased from Messrs. Sensiba Brothers and excavated by the American Museum in 1906."
After Osborn
Fig. 30.—The Dinosaur Mummy. Skeleton of a Trachodon preserving the skin impressions over a large part of the body.
THE DINOSAUR "MUMMY."
We all believe that the Dinosaurs existed. But to realize it is not so easy. Even with the help of the mounted skeletons and restorations, they are somewhat unreal and shadowy beings in the minds of most of us. But this "dinosaur mummy" sprawling on his back and covered with shrunken skin—a real specimen, not restored in any part—brings home the reality of this ancient world even as the mummy of an ancient Egyptian brings home to us the reality of the world of the Pharaohs. The description of this unique skeleton by Professor Henry Fairfield Osborn first appeared in the Museum Journal for January 1911.[17]
"Two years ago (1908) through the Jesup Fund, the Museum came into possession of a most unique specimen discovered in August 1908, by the veteran fossil hunter Charles H. Sternberg of Kansas. It is a large herbivorous dinosaur of the closing period of the Age of Reptiles and is known to palaeontologists as Trachodon or more popularly as the 'duck-billed dinosaur.'
"The skeleton or hard parts of these very remarkable animals had been known for over forty years, and a few specimens of the epidermal covering, but it was not until the discovery of the Sternberg specimen that a complete knowledge of the outer covering of these dinosaurs was gained. It appears probable that in a number of cases these priceless skin impressions were mostly destroyed in removing the fossil specimens from their surroundings because the explorers were not expecting to find anything of the kind. Altogether seven specimens have been discovered in which these delicate skin impressions were partly preserved, but the 'Trachodon mummy' far surpasses all the others, as it yields a nearly complete picture of the outer covering.
"The reason the Sternberg specimen (Trachodon annectens) may be known as a dinosaur 'mummy' is that in all the parts of the animal which are preserved (i.e. all except the hind limbs and the tail), the epidermis is shrunken around the limbs, tightly drawn along the bony surfaces, and contracted like a great curtain below the chest area. This condition of the epidermis suggests the following theory of the deposition and preservation of this wonderful specimen, namely: that after dying a natural death the animal was not attacked or preyed upon by its enemies, and the body lay exposed to the sun entirely undisturbed for a long time, perhaps upon a broad sand flat of a stream in the low-water stage; the muscles and viscera thus became completely dehydrated, or desiccated by the action of the sun, the epidermis shrank around the limbs, was tightly drawn down along all the bony surfaces, and became hardened and leathery, on the abdominal surfaces the epidermis was certainly drawn within the body cavity, while it was thrown into creases and folds along the sides of the body owing to the shrinkage of the tissues within. At the termination of a possible low-water season during which these processes of desiccation took place, the 'mummy' may have been caught in a sudden flood, carried down the stream and rapidly buried in a bed of fine river sand intermingled with sufficient elements of clay to take a perfect cast or mold of all the epidermal markings before any of the epidermal tissues had time to soften under the solvent action of the water. In this way the markings were indicated with absolute distinctness, ... the visitor will be able by the use of the hand glass to study even the finer details of the pattern, although of course there is no trace either of the epidermis itself, which has entirely disappeared, or of the pigmentation or coloring, if such existed.
"Although attaining a height of fifteen to sixteen feet the trachodons were not covered with scales or a bony protecting armature, but with dermal tubercles of relatively small size, which varied in shape and arrangement in different species, and not improbably associated with this varied epidermal pattern there was a varied color pattern. The theory of a color pattern is based chiefly upon the fact that the larger tubercles concentrate and become more numerous on all those portions of the body exposed to the sun, that is, on the outer surfaces of the fore and hind limbs, and appear to increase also along the sides of the body and to be more concentrated on the back. On the less exposed areas, the under side of the body and the inner sides of the limbs, the smaller tubercles are more numerous, the larger tubercles being reduced to small irregularly arranged patches. From analogy with existing lizards and snakes we may suppose, therefore, that the trachodons presented a darker appearance when seen from the back and a lighter appearance when seen from the front.
After Osborn
Fig. 31.—The Dinosaur Mummy. Detail of skin of under side of body.
Fig. 32.—Skin impression from the tail of a Trachodon. The impressions appear to have been left by horny scutes or scales, not overlapping like the scales on the body of most modern reptiles, but more like the scutes on the head of a lizard.
Fig. 33.—Skull of Gila Monster (Heloderma), for comparison of surface with skin impressions of Trachodon. Enlarged to 4/3.
"The thin character of the epidermis as revealed by this specimen favors also the theory that these animals spent a large part of their time in the water, which theory is strengthened by the fact that the diminutive fore limb terminates not in claws or hoofs, but in a broad extension of the skin, reaching beyond the fingers and forming a kind of paddle.[18] The marginal web which connects all the fingers with each other, together with the fact that the lower side of the fore limb is as delicate in its epidermal structure as the upper, certainly tends to support the theory of the swimming rather than the walking or terrestrial function of this fore paddle as indicated in the accompanying preliminary restoration that was made by Charles R. Knight working under the writer's direction. One is drawn in the conventional bipedal or standing posture while the other is in a quadrupedal pose or walking position, sustaining or balancing the fore part of the body on a muddy surface with its fore feet. In the distant water a large number of animals are disporting themselves.
"The designation of these animals as the 'duck-billed' dinosaurs in reference to the broadening of the beak, has long been considered in connection with the theory of aquatic habitat. The conversion of the fore limb into a sort of paddle, as evidenced by the Sternberg specimen, strengthens this theory.
"This truly wonderful specimen, therefore, nearly doubles our previous insight into the habits and life of a very remarkable group of reptiles."
Saurolophus, Corythosaurus. In the latest Cretaceous formation, the Lance or Triceratops beds, all the duck-billed dinosaurs are much alike, and are referred to the single genus Trachodon. In somewhat older formations of the Cretacic period there were several different kinds. Saurolophus has a high bony spine rising from the top of the skull; in Corythosaurus there is a thin high crest like the crown of a cassowary on top of the skull, and the muzzle is short and small giving a very peculiar aspect to the head. Complete skeletons of these two genera are exhibited in the Dinosaur Hall; the Corythosaurus is worthy of careful study, as the skin of the body, hind limbs and tail, the ossified tendons, and even the impressions of the muscular tissues in parts of the body and tail, are more or less clearly indicated.
After Brown
Fig. 34.—Skeleton of Saurolophus, from Upper Cretacic of Alberta.
These Duck-billed Dinosaurs probably ranged all over North America and the northerly portions of the Old World during the later Cretacic. Fragmentary remains have been found in New Jersey and southward along the Atlantic coast. A partial skeleton was described many years ago by Leidy under the name of Hadrosaurus and restored and mounted in the museum of the Philadelphia Academy of Sciences. Telmatosaurus of the Gosau formation in Austria also belongs to this group, and fragmentary remains have been found in the upper Cretacic of Belgium, England and France.
FOOTNOTES:
[16] Brown, Barnum. "The Trachodon Group." Amer. Mus. Jour. Vol. viii, pp. 51-56, plate and 3 text figs., 1908.
[17] Osborn, Henry Fairfield, "Dinosaur Mummy" Amer. Mus. Jour. Vol. xi, pp. 7-11, illustrated, Jan. 1911.
[18] There is some doubt whether this was really the condition during life. W.D.M.
Chapter VIII.[ToC]
THE BEAKED DINOSAURS (Continued.)
C. The Armored Dinosaurs—Stegosaurus, Ankylosaurus.
Sub-Order Stegosauria.
This group of dinosaurs is most remarkable for the massive bony armor plates, crests or spines covering the body and tail. They were more or less completely quadrupedal instead of bipedal, with straight post-like limbs and short rounded hoofed feet adapted to support the weight of the massive body and heavy armature. Although so different superficially from the bird-footed biped Iguanodonts they are evidently related to them, for the teeth are similar, and the horny beak, the construction of the pelvis, the three-toed hind foot and four-toed front foot all betray relationship. From what we know of them it seems probable that they evolved from Iguanodont ancestors, developing the bony armor as a protection against the attacks of carnivorous dinosaurs, and modifying the proportions of limbs and feet to enable them to support its weight. They were evidently herbivorous and some of them of gigantic size. Smaller kinds with less massive armor have been found in Europe but the largest and most extraordinary members of this strange race are from North America.
STEGOSAURUS.
This extraordinary reptile equalled the Allosaurus in size, and bore along the crest of the back a double row of enormous bony plates projecting upward and somewhat outward alternately to one side and the other. The largest of these plates situated just back of the pelvis were over two feet high, two and a half long, thinning out from a base four inches thick. The tail was armed with four or more stout spines two feet long and five or six inches thick at the base. In the neck region and probably elsewhere the skin had numerous small bony nodules and some larger ones imbedded in its substance or protecting its surface. The head was absurdly small for so huge an animal, and the stiff thick tail projected backward but was not long enough to reach the ground. The hind limbs are very long and straight, the fore limbs relatively short, and the short high arched back and extremely deep and compressed body served to exaggerate the height and prominence of the great plates. The surface of these plates, covered with a network of blood-vessels, shows that they bore a covering of thick horny skin during life, which probably projected as a ridge beyond their edges and still further increased their size. The spines of the tail, also, were probably cased in horn.
This extraordinary animal was a contemporary of the Brontosaurus and Allosaurus, and its discovery was one of the great achievements of the late Professor Marsh. The skeletons which he described are mounted in the Yale and National Museums. Another skeleton was found in the famous Bone-Cabin Quarry, near Medicine Bow, Wyoming, by the American Museum Expedition of 1901. This skeleton, at present withdrawn from lack of space, will be mounted in the Jurassic Dinosaur Hall in the new wing now under construction.
After Brown
Fig. 35.—Skull and lower jaw of Armored Dinosaur Ankylosaurus, from Upper Cretacic (Edmonton formation) of Alberta. Left side view.
ANKYLOSAURUS.
Related to Stegosaurus, equally huge, but very different in proportions and character of its armor was the Ankylosaurus of the late Cretacic. This animal, a contemporary of the Tyrannosaurus and duck-billed dinosaurs was more effectively though less grotesquely armored than its more ancient relative. The body is covered with massive bony plates set close together and lying flat over the surface from head to tip of tail. While the stegosaur's body was narrow and compressed, in this animal it is exceptionally broad and the wide spreading ribs are coössified with the vertebrae, making a very solid support for the transverse rows of armor plates. The head is broad triangular, flat topped and solidly armored, the plates consolidated with the surface of the skull and overhanging sides and front, the nostrils and eyes overhung by plates and bosses of bone; and the tail ended in a blunt heavy club of massive plates consolidated to each other and to the tip of the tail vertebrae. The legs were short, massive and straight, ending probably in elephant-like feet. The animal has well been called "the most ponderous animated citadel the world has ever seen" and we may suppose that when it tucked in its legs and settled down on the surface it would be proof even against the attacks of the terrible Tyrannosaur.
After Brown
Fig. 36.—Ankylosaurus, top view of skull in fig. 35.
This marvellous animal was made known to science by the discoveries of the Museum parties in Montana and Alberta under Barnum Brown. Fragmentary remains of smaller relatives had been discovered by earlier explorers but nothing that gave any adequate notion of its character or gigantic size. From a partial skeleton discovered in the Hell Creek beds of Montana, and others in the Edmonton and Belly River formations of the Red Deer River, Alberta, it has been possible to reconstruct the entire skeleton of the animal, save for the feet, and to locate and arrange most of the armor plates exactly. A skeleton mount from these specimens will shortly be constructed for the Cretaceous Dinosaur Hall.
Scelidosaurus, Polacanthus, etc. Various armored dinosaurs, of smaller size and less heavily plated, have been described from the Jurassic, Comanchic and Cretacic formations of Europe. The best known are Scelidosaurus of the Lower Jurassic of England, and Polacanthus of the Comanchic (Wealden). Stegopelta of the Cretaceous of Wyoming is more nearly related to Ankylosaurus.
Chapter IX.[ToC]
THE BEAKED DINOSAURS (Concluded.)
D. The Horned Dinosaurs, Triceratops, Etc.
Sub-Order Ceratopsia.
In 1887 Professor Marsh published a brief notice of what he supposed to be a fossil bison horn found near Denver, Colorado. Two years later the explorations of the lamented John B. Hatcher in Wyoming and Montana resulted in the unexpected discovery that this horn belonged not to a bison but to a gigantic horned reptile, and that it belonged not in the geological yesterday as at first thought, but in the far back Cretacic, millions of years ago. For Mr. Hatcher found complete skulls, and later secured skeletons, clearly of the Dinosaurian group, but representing a race of dinosaurs whose existence, or at least their extraordinary character, had been quite unsuspected. It appeared indeed that certain teeth and skeleton bones previously discovered by Professor Cope were related to this new type of dinosaur, but the fragments known to the Philadelphia professor gave him no idea of what the animal was like, although with his usual acumen he had discerned that they differed from any animal known to science and registered them as new under the names of Agathaumas 1873 and Monoclonius 1876. Professor Marsh re-named his supposed bison "Ceratops" (i.e. "horned face") and gave to the closely related skulls discovered by Mr. Hatcher the name of Triceratops (i.e. "three horned face"), while to the whole group he gave the name of Ceratopsia.
Fig. 37.—Skulls of Horned Dinosaurs. The lower row, Ceratops, Styracosaurus, Monoclonius, are from the Middle Cretacic (Belly River formation) of Alberta; Anchiceratops is from the Upper Cretacic (Edmonton formation) of Alberta; Triceratops and Torosaurus from the uppermost Cretacic (Lance formation) of Wyoming.
These were the first of a long series of discoveries which through scientific and popular descriptions have made the Horned Dinosaurs familiar to the world. Most of them are still very imperfectly known, and of their evolution and earlier history we know very little as yet. But we can form a fairly correct idea of their general appearance and habits and of the part they played in the world of the late Cretacic. So far as known they were limited to North America. The most striking feature of the Horned Dinosaurs is the gigantic skull, armed with a pair of horns over the orbits and a median horn on the nasal bones in front, and with a great bony crest projecting at the back and sides. In some species the skull with its bony frill attains a length of seven or even eight feet and about three feet width; the usual length is five or six feet and the width about three. In the best known genus, Triceratops, the paired horns are long and stout and the front horn quite short or almost absent, while in Monoclonius these proportions are reversed, the front horn being long while the paired horns are rudimentary.
The teeth are in a single row but are broadened out into a wide grinding surface. The animal was quadrupedal, with short massive limbs and rounded elephantine feet tipped with hoofs, three in the hind foot, four in the fore foot, a short massive tail that could hardly reach the ground, a short broad-barrelled body and a short neck completely hidden on top and sides by the overhanging bony frill of the skull. In many respects these animals are suggestive far more than any other dinosaurs, of the great quadrupeds of Tertiary and modern times, rhinoceroses, hippopotami, titanotheres and elephants, as in the horns they suggest the bison. For this reason although less gigantic than the Brontosaurus or Tyrannosaurus, less grotesque perhaps, than the Stegosaurus, they are more interesting than any other dinosaurs. While thus departing far from the earlier type of the beaked dinosaurs (the Iguanodonts) they are evidently descended from them.
Fig. 38.—Skull of Triceratops from the Lance formation in Wyoming, one-eighteenth natural size. The length of the horns is 2 feet, 9½ inches. The rostral bone or beak, and the lower jaw, are lacking; in the illustration on the cover they have been restored in outline. This fine skull was discovered by George M. Sternberg, and purchased for the Museum by Mr. Charles Lanier in 1909.
TRICERATOPS.
This is the best known of the Horned Dinosaurs, as various skulls and partial skeletons have been found from which it has been possible to reconstruct the entire animal. There is a mounted skeleton in the National Museum, another will shortly be mounted in the American Museum, and there are skulls in several American and European museums.
Triceratops exceeded the largest rhinoceroses in bulk, equalling a fairly large elephant, but with much shorter legs. The great horns over the eyes projected forward or partly upward; in one of our skulls they are 33½ inches long. During life they were probably covered with horn increasing the length by six inches or perhaps a foot. The ball-like condyle for articulation of the neck lies far underneath, at the base of the frill, almost in the middle of the skull.
Fig. 39.—Skull of Monoclonius, a horned dinosaur from the Cretacic (Belly River formation) of Alberta. One-fifteenth natural size. The horns over the eyes are rudimentary, and the nasal horn large, reversing the proportions in Triceratops.
Monoclonius, Ceratops, etc. The Triceratops and another equally gigantic Horned Dinosaur, Torosaurus, were the last survivors of their race. In somewhat older formations of Cretacic age are found remains of smaller kinds, some of them ancestors of these latest survivors, others collaterally related. None of these have the bony frill completely roofing over the neck as it does in Triceratops. There is always a central spine projecting backwards and widening out at the top to the bony margin of the frill which sweeps around on each side to join bony plates that project from the sides of the skull top. This encloses an open space or "fenestra," so that the neck was not completely protected above. Sometimes the margin of the frill is plain, at other times it carries a number of great spikes, like a gigantic Horned Lizard (Phrynosoma).
Fig. 40.—Outline sketch restoration of Triceratops, from the mounted skeleton in the National Museum.
In Ceratops the horns over the eyes are large and the nasal horn small. In Monoclonius the nasal horn is large and those over the eyes are rudimentary. The great variety of species that has been found in recent years shows that these Horned Dinosaurs were a numerous and varied race of which as yet we know only a few. Of their evolution we have little direct knowledge, but probably they are descended from the Iguanodonts and Camptosaurs of the Comanchic, and their quadrupedal gait, huge heads, short tails and other peculiarities are secondary specializations, their ancestors being bipedal, long-tailed, small headed and hornless.
The fine skulls of Triceratops, Monoclonius, Ceratops and Anchiceratops in the Museum collections illustrate the variety of these remarkable animals. Complete skeletons of the first two genera are being prepared for mounting and exhibition.
Chapter X.[ToC]
GEOGRAPHICAL DISTRIBUTION OF DINOSAURS.
Remains of Dinosaurs have been found in all the continents, but chiefly in Europe and North America. Explorations in other parts of the world have not as yet been sufficient to show whether or not each continent developed especial kinds peculiar to it, nor to afford any reliable evidence as to whether the relations of the continents were different during the Mesozoic. Thus far, the Carnivorous group seems most widespread, for it alone has been found in Australia. The Sauropods or Amphibious Dinosaurs have been found in Europe, North America, India, Madagascar, Patagonia, and Africa, sufficient to show that their distribution was world wide with the possible exception of Australia, and probable exception of most oceanic islands (few of the modern oceanic islands existed at that time although there may well have been many others no longer extant). The Beaked Dinosaurs are more limited in their distribution, for none of them so far as at present known reached Australia or South America. But in the present stage of discovery it would be rash to conclude that they were surely limited to the regions where they have been discovered. It is not wholly clear as yet whether the Dinosaurian fauna that flourished at the end of the Jurassic in the north survived to the Upper Cretacic in the southern continents, but present evidence points that way, and indicates that the girdle of ocean which during the Cretacic depression encircled the northern world, formed a barrier which the Cretacic dinosaurian fauna never succeeded in crossing.
The earlier groups of Beaked Dinosaurs are found in both Europe and America, and in the Cretacic the Duck-billed and Armored groups are represented in both regions. The Horned Dinosaurs, however, are known with certainty only from North America.
While most of the important fossil specimens in this country have been found in the West, more fragmentary remains have been found on the Atlantic sea-board, and it is probable that they ranged all over the intervening region, wherever they found an environment suited to their particular needs.
Chapter XI.[ToC]
COLLECTING DINOSAURS.
How and Where They are Found.
The visitor who is introduced to the dinosaurs through the medium of books and pictures or of the skeletons exhibited in the great museums, finds it hard—well nigh impossible—to realize their existence. However willing he may be to accept on faith the reconstructions of the skeletons, the restorations of the animals and their supposed environment, it yet remains to him somewhat of a fairy-tale, a fanciful imaginative world peopled with ogres and dragons and belonging to the unreal "once upon a time" which has no connection with the ever present workaday world in which we live. Birds and squirrels, rabbits and foxes belong to this real world because he has seen them in his walks through the woods; even elephants and rhinoceroses, though his acquaintance be limited to menagerie specimens, seem fairly real—although one recalls the farmer's comment on first seeing a giraffe in the Zoological park: "There aint no sich animal." But dinosaurs—one easily realizes the state of mind that prompts the inquiry so often made by visitors to the Dinosaur Hall:—"they make these out of plaster, don't they?" So far as is consistent with good taste, the aim of the American Museum has been to enable the visitor to see for himself how much of plaster reconstruction there is to each skeleton, and to explain in the labels what the basis was for the reconstructed parts.
How They are Found. But to the collector these extinct animals are real enough. As he journeys over the western plains he sees the various living inhabitants thereof, birds and beasts, as well as men, pursuing their various modes of life; here and there he comes across the scattered skeletons or bones of modern animals lying strewn upon the surface of the ground or half buried in the soil of a cut bank. In the shales or sandstones that underlie the soil he finds the objects of his search, skeletons or bones of extinct animals, similarly disposed, but buried in rock instead of soft soil, and exposed in cañons and gullies cut through the solid rock. Each rock formation, he knows by precept and experience, carries its own peculiar fauna, its animals are different from those of the formation above and from those in the formation below. Days and weeks he may spend in fruitless search following along the outcrop of the formation, through rugged badlands, along steep cañon walls, around isolated points or buttes, without finding more than a few fragments, but spurred on by vivid interest and the rainbow prospect of some new or rare find. Finally perhaps, after innumerable disappointments, a trail of fragments leads up to a really promising prospect. A cautious investigation indicates that an articulated skeleton is buried at this point, and that not too much of it has "gone out" and rolled in weathered fragments down the slope. For the tedious and delicate process of disinterring the skeleton from the rock he will need to keep ever in mind the form and relations of each bone, the picture of the skeleton as it may have been when buried. The heavy ledges above are removed with pick and shovel, often with help of dynamite and a team and scraper. As he gets nearer to the stratum in which the bones lie the work must be more and more careful. A false blow with pick or chisel might destroy irreparably some important bony structure. Bit by bit he traces out the position and lay of the bones, working now mostly with awl and whisk-broom, uncovering the more massive portions, blocking out the delicate bones in the rock, soaking the exposed surfaces repeatedly with thin "gum" (mucilage) or shellac, channeling around and between the bones until they stand out on little pedestals above the quarry floor. Then, after the gum or shellac has dried thoroughly and hardened the soft parts, and the surfaces of bone exposed are further protected by pasting on a layer of tissue paper, it is ready for the "plaster jacket." This consists of strips of burlap dipped in plaster-of-paris and pasted over the surface of each block until top and sides, all but the pedestal on which it rests, are completely cased in, the strips being pressed and kneaded close to the surface of the block as they are laid on. When this jacket sets and dries the block is rigid and stiff enough to lift and turn over; the remains of the pedestal are trimmed off and the under surface is plastered like the rest. With large blocks it is often necessary to paste into the jacket, on upper or both sides, boards, scantling or sticks of wood to secure additional rigidity. For should the block "rack," or become shattered inside, even though no fragments were lost, the specimen would be more or less completely ruined.
Fig. 41.—A Dinosaur skeleton, prospected and ready for encasing in plaster bandages and removal in blocks. (Corythosaurus, Red Deer River, Alberta.)
The next stage will be packing in boxes with straw, hay or other materials, hauling to the railway and shipment to New York.
Arrived at the Museum, the boxes are unpacked, each block laid out on a table, the upper side of its plaster jacket softened with water and cut away, and the preparation of the bone begins. Always it is more or less cracked and broken up, but the fragments lie in their natural relations. Each piece must be lifted out, thoroughly cleaned from rock and dirt, and the fractured surfaces cemented together again. Parts of bones, especially the interior, are often rotted into dust while the harder outer surface is still preserved. The dust must be scraped out, the interior filled with a plaster cement, and the surface pieces re-set in position. Very often a steel rod is set into the plaster filling the interior of a bone, to secure additional strength.
After this preparation is completed, each part being soaked repeatedly with shellac until it will absorb no more, the bones can be handled and laid out for study or exhibition. Then, if they are to be mounted for a fossil skeleton, comes the work of restoring the missing parts. For this a plaster composition is used.
Where only parts of one side are missing the corresponding parts of the other side are used for model; where both sides are missing, other individuals or nearly related species may serve as a guide. But it is seldom wise to attempt restoration of a skeleton unless at least two-thirds of it is present; composite skeletons made up of the remains of several or many individuals, have been attempted, but they are dangerous experiments in animals so imperfectly known as are most of the dinosaurs. There is too much risk of including bones that pertain to other species or genera, and of introducing thereby into the restoration a more or less erroneous concept of the animal which it represents. The same criticism applies to an overly large amount of plaster restoration.
Fig. 42.—Bone-Cabin Draw on Little Medicine River north of Medicine Bow, Wyoming. The location of the quarry is indicated by the stack of crated specimens on the left, and close to it the low sod-covered shack where the collecting party lived. Beyond the draw lies the flat rolling surface of the Laramie Plains and on the southern horizon the Medicine Bow Range with Elk Mountain at the center.
In some instances the missing parts of a skeleton are not restored, because, even though but a small part be gone, we have no good evidence to guide in its reconstruction. This gives an imperfect and sometimes misleading concept of what the whole skeleton was like, but it is better than restoring it erroneously. Usually with the more imperfect skeletons, a skull, a limb or some other characteristic parts may be placed on exhibition but the remainder of the specimen is stored in the study collections.
Fig. 43.—American Museum party at Bone-Cabin Quarry, 1899. Seated, left to right Walter Granger, Professor H.F. Osborn, Dr. W.D. Matthew; standing, F. Schneider, Prof. R.S. Lull, Albert Thomson, Peter Kaison.
Where They are Found. The chief dinosaur localities in this country are along the flanks of the Rocky Mountains and the plains to the eastward, from Canada to Texas. Not that dinosaurs were any more abundant there than elsewhere. They probably ranged all over North America, and different kinds inhabited other continents as well. But in the East and the Middle West, the conditions were not favorable for preserving their remains, except in a few localities. Formations of this age are less extensive, especially those of the delta and coast-swamps which the dinosaurs frequented. And where they do occur, they are largely covered by vegetation and cannot be explored to advantage. In the arid Western regions these formations girdle the Rockies and outlying mountain chains for two-thousand miles from north to south, and are extensively exposed in great escarpments, river cañons and "badland" areas, bare of soil and vegetation and affording an immense stretch of exposed rock for the explorer. Much of this area indeed is desert, too far away from water to be profitably searched under present conditions, or too far away from railroads to allow of transportation of the finds at a reasonable expense. Fossils are much more common in certain parts of the region, and these localities have mostly been explored more or less thoroughly. But the field is far from being exhausted. New localities have been found and old localities re-explored in recent years, yielding specimens equal to or better than any heretofore discovered. And as the railroad and the automobile render new regions accessible, and the erosion of the formations by wind and rain brings new specimens to the surface, we may look forward to new discoveries for many years to come.
In other continents, except in Europe, there has been but little exploration for dinosaurs. Enough is known to assure us that they will yield faunæ no less extensive and remarkable than our own. We are in fact only beginning to appreciate the vast extent and variety of these records of a past world.
In a preceding chapter it was shown that the chief formations in which dinosaur remains have been found belong to the end of the Jurassic and the end of the Cretacic periods. The Jurassic dinosaur formations skirt the Rockies and outlying mountain ranges but are often turned up on edge and poorly exposed, or barren of fossils. The richest collecting ground is in the Laramie Plains, between the Rockies and the Laramie range in south-central Wyoming, but important finds have also been made in Colorado and Utah. The Cretaceous Dinosaur formations extend somewhat further out on the plains to the eastward, and the best collecting regions thus far explored are in eastern Wyoming, central Montana and in Alberta, Canada.